Method of electrodepositing a metal layer on rubber



y 1951 E. L. SCHOLL 2,551,343

METHOD OF ELECTRODEPOSITING A METAL LAYER 0N RUBBER Original Filed Oct.19, 1946 INVENTOR. [1/7000 1. 067/011 4M1 mm .A Tram/5y Patented May 1,1951 UNITED STATES PATENT OFFICE METHOD OF ELECTRODEPOSITING A METALLAYER ON RUBBER Original application October 19, 1946, Serial No.704,505. Divided and this application November 23, 1948, Serial No.61,561

1 Claim. 1

This invention relates to a method of making a composite article, and inparticular it relates to an improved method of bonding a layer of anelectrodeposited metal to a rubber-like material.

This application is a division of my prior application Serial No.704,505, filed October 19, 1946.

In bonding rubber to metal, many known processes are available. Theseprocesses usually involve vulcanization of the rubber while in contactwith the metal, but in electrodepositing a layer of metal against arubber base the rubber is not simultaneously vulcanized, andconsiderable difficulty is ordinarily encountered in securing a strongadhesion between the rubber and the metal.

In accordance with the practice of my invention, I have found that ahigh degree of adhesion can be obtained between the electrodepositedmetal and a rubber-like material in the form of an organic elasticmaterial of the general nature of rubber. This is accomplished byspecially treating the surface of the rubber-like material before itreceives the electrodeposited metal that is to be secured thereto.

In general the invention comprises the treatment of an elastic materialwith a solution of either phosphorous trichloride, chloroacetylchloride, or bromine, allowing this coating to dry, applying aconductive layer such as graphite to the treated surface, and thenelectrodepositing a layer of metal against the prepared surface.

Among the objects of my invention are to provide a method ofelectrodepositing a layer of metal in bonded relation to the surface ofa rubber-like material; to provide a method of bondin a rubber-likematerial and an electrodeposited metal together so that a high degree ofbond may be obtained notwithstanding considerable variability in theshape of the rubber-like material against which the metal iselectrodeposited; and, to provide such a method of bonding which may beaccomplished expeditiously and economically.

These and other objects and advantages of my invention will appear morefully in the following detailed description when considered inconnection with the accompanying drawing, in

which:

The figure shown is a perspective view, partly broken away, illustratinga composite article made in accordance with the method of my invention.

With reference to the drawing I show an embodiment of my invention inthe form of an elastic rubber-like material to which is bonded anelectrodepositedlayer of metal2. The elastic material I may beidentified as an organic elastic material of the general nature ofrubber. This definition is intended to include natural rubber as well asthose synthetic rubbers such a Neoprene (polymerized chloroprene), BunaS (copolymerized butadiene and styrene), and Buna N (copolymerizedbutadiene and acylonitrile). It is to be understood that these elasticmaterials refer to a compounded stock such as used in conventionalapplications of these rubber or synthetic rubbers. In other words theelastic materials include such reinforcing agents as carbon blacktogether with vulcanizing agents, accelerators, and the like. Whilesatisfactory adhesion may be obtained between the electrodeposited metaland the elastic material, with the elastic material in an unvulcanizedstate, it is preferable that the elastic material be vulcanized in orderto improve its physical properties. Although the rubber-like material Iis illustrated in the drawing as a flat block or sheet, it is to beunderstood that the rubber-like material may be in the form of a curvedsurface or may have various irregular shapes.

The degree of adhesion between the electrodeposited metal 2 and theelastic material I may be increased substantially in accordance with thepresent invention by subjecting the elastic material to a specifictreatment prior to the electrodeposition of the metal. This treatmentconsists of applying to the surface of the elastic material 1 eitherphosphorous trichloride, chloroacetyl chloride, or bromide to form atreated surface 3. To facilitate this treatment the chemical agent isreduced to solution form, and may be applied conveniently by spraying,painting, or dipping the article in such solution.

The phosphorous trichloride is used in concentrated form or it may beused as a solution in ether, carbon tetrachloride, or carbon disulfide.The concentration of the phosphorous trichloride in the solution shouldbe at least 50%. The chloroacetyl chloride is used in concentrated form.Bromine is used as a /2% to 10% solution in a suitable solvent such ascarbon disul fide, carbon tetrachloride, or ether.

After the rubber-like material is treated with the chemical agent, it issubjected to vulcanization in accordance with conventional vulcanizationmethods. Good results can also be ob- 3 tained by vulcanizing therubber-like material prior to its treatment with the chemical agent.

After the rubber-like material I is vulcanized and then treated and thesolution dried, or after the solution is applied and the rubber-likematerial is then vulcanized, the treated surface 3 is coated with alayer 4 capable of rendering the surface electrically conducting.Ordinarily this is accomplished by applying over the treated surface 3,by means of a brush, a layer 4 of finely divided particles of graphite.It is to be understood that other conductive materials may be used forthis purpose, such, for example, .as finely divided particles of iron orbronze. After the electrically conductive layer 4 is applied, the coatedarticle is placed in an electrolyte and a metal layer 2 i depositedthereon. The metal to be electrodeposited is preferably iron. Goodadhesion results are also obtained by the electrodeposition of nickel.Conventional electrodeposition baths may be used for this purpose.

I have, therefore, provided through the present invention a novel methodof adhering an electrodeposited layer of metal to an elastic materialresulting in a very stron bond which require a pull as high as 1200pounds per square inch in shear, in order to separate the layers.

As thus described, an electrodeposited layer of metal can be firmlybonded to an elastic layer, or to some other non-metallic base memberthrough the means of an interposing layer of elastic material, by aplurality of steps each of which is necessary in order to provide anoptimum degree of adhesion between the adjacent layers.

While I have shown a preferred method of practicing my invention it isto be understood that it is susceptible of those modifications whichappear obviously within the spirit of my invention and as appearing inthe scope of the appended claim.

Having thus described my invention, what I claim and desire to protectby Letters Patent is:

The method of bonding an electrodeposited layer of metal to rubber so asto secure a strong bond therebetween, comprising the steps of providinga layer of rubber, treating a surface thereof with chloroacetylchloride, then coating the treated surface with electrically conductiveparticles to render it electrically conductive, and electrodepositingthereon a layer of metal selected from the group consisting of iron andnickel in direct contact with the rubber so that the metal is bondeddirectly and strongly to the treated surface of the rubber.

ELVVOOD L. SCHOLL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 889,807 Reynolds June 2, 19081,624,575 Biddle Apr. 12, 1927 2,078,911 Merrill Apr. 27, 1937 FOREIGNPATENTS Number Country Date 710 Great Britain of 1909 429,557 GreatBriain of 1935

